diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 2919a2e919388cd572a7e99559c90e92dc544a28..edab81c131823ea6b863ea9373575c42df56b2b7 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -89,6 +89,7 @@ parameter is applicable:
SPARC Sparc architecture is enabled.
SWSUSP Software suspend (hibernation) is enabled.
SUSPEND System suspend states are enabled.
+ FTRACE Function tracing enabled.
TS Appropriate touchscreen support is enabled.
USB USB support is enabled.
USBHID USB Human Interface Device support is enabled.
@@ -2173,6 +2174,9 @@ and is between 256 and 4096 characters. It is defined in the file
st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
See Documentation/scsi/st.txt.
+ stacktrace [FTRACE]
+ Enabled the stack tracer on boot up.
+
sti= [PARISC,HW]
Format: <num>
Set the STI (builtin display/keyboard on the HP-PARISC
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 44020f31bd817a6dbf1f038f2d9b6500db942281..6b0db53caa7d464b539579937d9dc1e17b000a63 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -86,6 +86,14 @@ static inline void ftrace_stop(void) { }
static inline void ftrace_start(void) { }
#endif /* CONFIG_FUNCTION_TRACER */
+#ifdef CONFIG_STACK_TRACER
+extern int stack_tracer_enabled;
+int
+stack_trace_sysctl(struct ctl_table *table, int write,
+ struct file *file, void __user *buffer, size_t *lenp,
+ loff_t *ppos);
+#endif
+
#ifdef CONFIG_DYNAMIC_FTRACE
/* asm/ftrace.h must be defined for archs supporting dynamic ftrace */
#include <asm/ftrace.h>
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index c83f566e940abaac4cdef8b7744746104aaabd38..6ac501a2dcc6aaf74d59b258f3f26a0b52f23b59 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -487,6 +487,16 @@ static struct ctl_table kern_table[] = {
.proc_handler = &ftrace_enable_sysctl,
},
#endif
+#ifdef CONFIG_STACK_TRACER
+ {
+ .ctl_name = CTL_UNNUMBERED,
+ .procname = "stack_tracer_enabled",
+ .data = &stack_tracer_enabled,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &stack_trace_sysctl,
+ },
+#endif
#ifdef CONFIG_TRACING
{
.ctl_name = CTL_UNNUMBERED,
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index d8bae6f4219ee32cc869fbaaee22a488553289e1..e2a4ff6fc3a6bb1509472dad03d0ad41df855748 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -244,10 +244,15 @@ config STACK_TRACER
This tracer works by hooking into every function call that the
kernel executes, and keeping a maximum stack depth value and
- stack-trace saved. Because this logic has to execute in every
- kernel function, all the time, this option can slow down the
- kernel measurably and is generally intended for kernel
- developers only.
+ stack-trace saved. If this is configured with DYNAMIC_FTRACE
+ then it will not have any overhead while the stack tracer
+ is disabled.
+
+ To enable the stack tracer on bootup, pass in 'stacktrace'
+ on the kernel command line.
+
+ The stack tracer can also be enabled or disabled via the
+ sysctl kernel.stack_tracer_enabled
Say N if unsure.
diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 0b863f2cbc8e3ff04c9ea8347f4ffb6795dab446..4842c969c7855ea749836b18f862cce95343f578 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -10,6 +10,7 @@
#include <linux/debugfs.h>
#include <linux/ftrace.h>
#include <linux/module.h>
+#include <linux/sysctl.h>
#include <linux/init.h>
#include <linux/fs.h>
#include "trace.h"
@@ -31,6 +32,10 @@ static raw_spinlock_t max_stack_lock =
static int stack_trace_disabled __read_mostly;
static DEFINE_PER_CPU(int, trace_active);
+static DEFINE_MUTEX(stack_sysctl_mutex);
+
+int stack_tracer_enabled;
+static int last_stack_tracer_enabled;
static inline void check_stack(void)
{
@@ -174,7 +179,7 @@ stack_max_size_write(struct file *filp, const char __user *ubuf,
return count;
}
-static struct file_operations stack_max_size_fops = {
+static const struct file_operations stack_max_size_fops = {
.open = tracing_open_generic,
.read = stack_max_size_read,
.write = stack_max_size_write,
@@ -272,7 +277,7 @@ static int t_show(struct seq_file *m, void *v)
return 0;
}
-static struct seq_operations stack_trace_seq_ops = {
+static const struct seq_operations stack_trace_seq_ops = {
.start = t_start,
.next = t_next,
.stop = t_stop,
@@ -288,12 +293,48 @@ static int stack_trace_open(struct inode *inode, struct file *file)
return ret;
}
-static struct file_operations stack_trace_fops = {
+static const struct file_operations stack_trace_fops = {
.open = stack_trace_open,
.read = seq_read,
.llseek = seq_lseek,
};
+int
+stack_trace_sysctl(struct ctl_table *table, int write,
+ struct file *file, void __user *buffer, size_t *lenp,
+ loff_t *ppos)
+{
+ int ret;
+
+ mutex_lock(&stack_sysctl_mutex);
+
+ ret = proc_dointvec(table, write, file, buffer, lenp, ppos);
+
+ if (ret || !write ||
+ (last_stack_tracer_enabled == stack_tracer_enabled))
+ goto out;
+
+ last_stack_tracer_enabled = stack_tracer_enabled;
+
+ if (stack_tracer_enabled)
+ register_ftrace_function(&trace_ops);
+ else
+ unregister_ftrace_function(&trace_ops);
+
+ out:
+ mutex_unlock(&stack_sysctl_mutex);
+ return ret;
+}
+
+static int start_stack_trace __initdata;
+
+static __init int enable_stacktrace(char *str)
+{
+ start_stack_trace = 1;
+ return 1;
+}
+__setup("stacktrace", enable_stacktrace);
+
static __init int stack_trace_init(void)
{
struct dentry *d_tracer;
@@ -311,7 +352,10 @@ static __init int stack_trace_init(void)
if (!entry)
pr_warning("Could not create debugfs 'stack_trace' entry\n");
- register_ftrace_function(&trace_ops);
+ if (start_stack_trace) {
+ register_ftrace_function(&trace_ops);
+ stack_tracer_enabled = 1;
+ }
return 0;
}